VFS_SET(9)

✨ VFS_SET(9) ✨

okay bestie, welcome to the Kernel Developer's Manual, page VFS_SET(9) 💖 this is the one that sets up your loadable file system's vfsconf and honestly? she's giving backstage-pass energy. let's get into it 🎀

🌸 NAME 🌸

VFS_SET — set up loadable file system vfsconf 👑

🦋 SYNOPSIS 🦋

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/module.h>
#include <sys/mount.h>

void
VFS_SET(struct vfsops *vfsops, fsname, int flags);

like, yes, those includes are non-negotiable, do not skip them, they are the fit check before the function call 💅

💖 DESCRIPTION 💖

so VFS_SET() does two things and it does them flawlessly. first, it creates a vfsconf structure for the loadable module using the vfsops you hand it, plus fsname, plus flags. then it declares that whole thing by calling DECLARE_MODULE(9), with vfs_modevent() as the event handler. that's it. that's the whole slay. ✨

now, the flags argument — she has OPTIONS, and here's every single one, no skips, no crumbs left behind:

• VFCF_STATIC — the file system should be statically available in the kernel.
• VFCF_NETWORK — network exportable file system.
• VFCF_READONLY — does not support write operations.
• VFCF_SYNTHETIC — pseudo file system, data does not represent on-disk files.
• VFCF_LOOPBACK — loopback file system layer.
• VFCF_UNICODE — file names are stored as Unicode.
• VFCF_JAIL — can be mounted from within a jail if allow.mount and allow.mount.<fsname> jail parameters are set.
• VFCF_DELEGADMIN — supports delegated administration if vfs.usermount sysctl is set to 1.
• VFCF_SBDRY — when in VFS method, the thread suspension is deferred to the user boundary upon arrival of stop action.

bestie note: VFCF_JAIL and VFCF_DELEGADMIN are conditional girlies — they only do their thing when those jail parameters / that vfs.usermount sysctl are set. don't come for me, that's literally what the page says 🙈

🧚 PSEUDOCODE 🧚

here's the vibe, copy the shape, not the letters:

/*
 * Fill in the fields for which we have special methods.
 * The others are initially null.  This tells vfs to change them to
 * pointers to vfs_std* functions during file system registration.
 */
static struct vfsops myfs_vfsops = {
        .vfs_mount =    myfs_mount,
        .vfs_root =     myfs_root,
        .vfs_statfs =   myfs_statfs,
        .vfs_unmount =  myfs_unmount,
};

VFS_SET(myfs_vfsops, myfs, 0);

see how she only fills in the fields with special methods? the rest stay null on purpose, and that's intentional — it tells vfs to swap them for pointers to vfs_std* functions during file system registration. main character behavior fr fr 💜

🔥 SEE ALSO 🔥

jail(2), jail(8), DECLARE_MODULE(9), vfs_modevent(9), vfsconf(9) — go read them, iykyk 🫶

👑 AUTHORS 👑

this manual page was written by Chad David <davidc@acns.ab.ca>. thank you chad, king behavior, we appreciate you 💐

and that's the whole page bestie, no notes, ate and left no crumbs 💅✨ this cutie came to you from Debian, dated August 16, 2018, filed under VFS_SET(9) — mwah, go write a file system 🌈🎀